Hydrocarbon conversion



Oct. 26, 1943. R. F. MARscHNER HYDROCARBON CONVERSION Filed Nov. 20,1940 Patented Oct. 26, 1943 2,332,924 nYDRocARBoN coNvEnsroN Robert F.Marsclmer, Chicago, Ill., assignor to Standard Oil Company, Chicago,Ill., a corporation of Indiana Application November 20, 1.940, SerialNo. 366,372 4 Claims. (Cl. ISB- 10) This invention' relates to theconversion of hydrocarbon materials to valuable motor fuels and relatesmore particularly to'the catalytic dehydrogenation of normally gaseousparaflinic hydrocarbons.

Thermal processes for the dehydrogenation of normally gaseous paraffnichydrocarbons, such.

as ethane, propane and butane, have been known in the art for some time,and have been practiced commercially. Such thermal processes,

however,' have Vvarious disadvantages, one of which is the degradationof the feed stock to paramnlc and/orolenic hydrocarbons of fewer carbonatoms per molecule, such as methane, for example, during the productionof the corresponding olefin and hydrogen. 4When catalyticdehydrogenation is employedJ under carefully controlled conditions, theolefins corresponding to the paraffinic hydrocarbons fed to the processare thev only conversion product in addition to hydrogen, but thepercent conversion is small and the amount of unreacted parafnichydrocarbon is large. This is probably due to a thermodynamichydrogenation-dehydrogenation equilibrium which inhibits the furtherdehydrogenation of paraflinic hydrocarbons at the temperature employedand the concentrations of oleflnvand/or hydrogen involved. If an attemptis made to increase the conversion by raising the'temperature, the samedisadvantages are encountered as in the thermal processes, i. e. much ofthe feed stock is degraded to less useful products 'such as methane andcarbon. Such side reactions lead to short catalyst life due to thedeposition of carbonaceous residue.

It is an object of my invention to provide a process for thesubstantially complete conversion of normally gaseous paraflinichydrocarbons to olenic hydrocarbons containing the same number of carbonatoms per molecule. Another object of my invention is to provide animproved process for the production of gasolines of high octane number.,My invention also has as its object the provision of va process for theconversion of normally gaseous hydrocarbons to normally liquidhydrocarbons of high antiknock value. A still further object isvtoprovide a combination process for the substantially completedehydrogenation of a normally gaseous hydrocarbon feed and the use ofthe dehydrogenation products in the production of gasolines of highoctane number gasoline. Further objects and advantages will becomeapparent as the description of my invention proceeds read in conjunctionwith the accompanying drawing which represents a flow diagram ofapparatus suitable for carrying out one embodiment of my process. f

Referring now to the drawing: A feed stock enters through line I 0. As a-feed stock I may employ a normally gaseous hydrocarbon, such as ethane,propane or butane, orv a mixture of any two or all three of thesehydrocarbons. A mixture of about two parts ethaneand one part propane isparticularly suitable. The hydrocarbons are preferably parailinic innature but the presence of minor amounts of oleflnic materials can betolerated. Methane and paraillns higher than butane are preferablyabsent, but small amounts of these are also permissible. The feed gasesare directed to heater Il by pump I2 and are heated to a temperaturewithin the range of fromabout 800 to 1400 F., the heated gases passingfrom heater Il to dehydrogenator i3 via line i4. Dehydrogenation iscarried out at pressures near atmospheric, say, Within the range of from0 to 50 pounds per square inch gauge, and at a vapor rate of from 500 to50,000 liquid volumes per volume of catalyst per hour, depending uponthe composition and preparation of the catalyst used. With ethane, atemperature of about 1300 F. and a rate of the order of 1000 liquidvolumes per volume of catalyst per hour represent good practice withmild catalysts. More active catalysts permit either lowering thetemperature or increasing the rate. A higher yield (based upon ethanereacted) is obtained by lowering the temperature in general and suchprocedure is preferred. With propane faster rates, for example 3000liquid volumes per volume of catalyst per hour and lower temperatures,for example, 1000 F. are preferred in the presence of active catalystssuch as those containing chromium. Butanes need only about 900 F. atabout 5000 liquid volumes perfvolume of catalyst per hour forsatisfactory conversion. Mixed gases in general are dehydrogenated underconditions lying be'- 1 twe'en the preferred conditions for theconstituents, but this is not an arithmetical relationship. Highertemperatures and higher rates than the mean values for temperature andrate thatwould be calculated for the gas composition appear to give lesspreferential dehydrogenation of the heavier paraffin.

As catalysts I prefer those having a selective dehydrogenating actionfor the paramns employed so that the corresponding olem'c materials areprepared without degradation of the feed stock to hydrocarbons of lowermolecular weight, and particularly those which do not degrade the feedstock to methane. Although certain catalysts are definitely moreselective than l paraiiins in the dehydrogenated gas. With the propercatalysts and conditions, the olen yields can usually be maintainedabove about 95%. My preferred catalysts include those containingaluminum, chromium, molybdenum, vanadium and/or tungsten, particularlytheir oxides. Mixtures of two or more of these compounds. can besuitably employed; for exampl, mixtures of chromia and alumina are verys able. One such catalyst suitable for the process consists of aboutfour parts of alumina and one part of chromic oxide by weight. Thesecatalysts may be supported catalysts such as, for example, chromic oxideon silica or promoted catalysts such as chromic oxide containing smallamounts of zinc, tin or zirconium oxides.

The dehydrogenated products together with the unconverted hydrocarbonsand the hydrogen produced during the reaction pass from dehydrogenatori3 through line i5 to alkylator 16. ln

` alkylator i6 the olefins produced in dehydrominum chloride-hydrocarboncomplex, formed by the reaction of anhydrous aluminum chloride withparaiiinic lor naphthenic hydrocarbons substantially free of aromatic orolefinic hydrocarbons in the presence of a .promoter such as hydrogenchloride at temperatures of from about 50 to about 250 F. The complexformed by the isomerization of light virgin naphthas having an end pointof, for example, 158 F., or by reaction with hydrogenated polymers suchas those of dibutylene or tributylene, using aluminum chloride as thereagent or isomerization agent, are particularly suitable. Aluminumbromide complexes are also suitable for my purpose and in the event thatoleilns having more than two carbon atoms per molecule are the onlyproducts A.formed during the dehydrogenation, sulfuric acid can beemployed. vI will further illustrateA my y process by reference to theuse. of the previously mentioned aluminum chloride-hydrocarbon complexin a continuous process. It is obvious, howdischarged through line i9.Other means for control, such'as coils within the alkylator, etc.. canbe suitably employed. Intimate contact between the reactants and thecatalysts is necessary and this may be accomplished by the use ofmechanical stirrer 20 as illustrated, or by other suitable means, suchas for example by passing the reactants and catalyst through a coil inalkylator I6 where the turbulent flow will cause the properV contactbetween the reactants and catalyst. Other methods which are suitableinclude the use of jet injectors, turbo mixers,

and in some cases packed towers can be employed.

Alkylator I6 is maintained at a temperature of from about 50 to about350 F., preferably about F., and under suitable pressures, for

example, from about 25 to about 750 pounds, so y isoparafinichydrocarbons such as isopentane,

isohexane, etc., are equally advantageous. Generally speaking, however,isopentane and isohexane form in themselves a desirable constituent ofhigh octane number motor and aviation fuels, and accordingly,'unlessthere is a surplus of such hydrocarbons available or the demand is greatfor hydrocarbons of higher molecular weight than isopentane andisohexane, these latter hydrocarbons will not be utilized foralkylation.

The isobutane or other isoparaiinic hydrocarbon can be obtained from anysuitable source (not shown) and injected through line 23, or it can bethe off-gas from a polymerization process (to be described in moredetail later) in which event the isobutane is injected into line 2l fromline 64. Dilution with normal butane is by no means prohibited and,generally speaking, isobutane from refinery sources will be found to bemixed with greater or lesser quantities of normal butane, so .that as apractical matter the isoparaiiinic feed to alkylator IB will containvaried amounts of unreactive hydrocarbons.

The reaction products including alkylate, unreacted hydrocarbons,hydrogen and catalyst are withdrawn from alkylator I6 through line 25 tosettler 26 wherein the separation is made between the catalyst, and thehydrocarbons and normally gaseous constituents, the catalyst beingwithdrawn: through line 21. If its activity for alkylation is spent'thecatalyst can be discarded by opening valve 28 in line 29, but since,generally speaking, it still is active for alkylation it can be returnedby opening valve 30 in line 3| which joins line 32. Alternately, a partof the catalyst can be withdrawn through line 29 for regeneration andthe remainder recycled to alkylator i6 through line 3| for use inconjunction with fresh catalyst introduced through line 32. Y

The hydrocarbon products together with unreacted hydrocarbons, hydrogenand any promoter present pass from settler 26 through line 33 tofractionator 34. Fractionator 34'is maintained under suitable conditionsof temperature and pressure so that a fractionation can be obtained 35and can be discharged from the system by opening valve 36 in line 31,but preferably is recycled to the alkylation reactor I by opening valve38 in line 39 which joins line 2 l In order to obtain further conversionto hydrocarbons of gasoline boiling range or to suppress the formationof hydrocarbons higher boiling than the gasoline range desired.hydrocarbons 4 lower boiling than butane. or if butanes were included inthe original feed stock, the hydrocarbons containing at least a portiono1' the butanes from fractionator 34 pass overhead through line 40 andcan be returned to the dehydrogenation system through line 4| by openingvalve 42 therein. The hydrogen chloride, of course, together with thehydrogen will also be included with these gases and it is desirable tosubject the gases to a caustic washing step or other means for removingor recovering the hydrogen chloride prior to the injection of the lightgases and hydrogen into the dehydrogenation system. On the other handthe light gases containing hydrogen can be utilized for hydrogenation aswill be described in detail, in which event valve 42 is closed and valve43 in line 44 is open. Alternately, a part can be recycled through line4| to line l0 and the remainder directed to the hydrogenationstepthrough line 44.

The hydrocarbons of gasoline boiling range, hereinafter referred to asalkylate, are withdrawn from fractionator 34 through line 45 todebutanizer 46 in which a part or all of the butane can be removeddepending upon the volatility desired in the ilnal product. \Thealkylate of gasoline boiling range with or without butane therein iswithdrawn from debutanizer 45 through line 41 and can be taken from thesystem by opening valve 48 in line 49 or directed to blending tank 52 byopening valve 50 in line 5| leading thereto. Since the isobutane orother isoparaillnic hydrocarbons were present in excess this can betaken overhead from debutanizer 4'6 through line 53 and recycled to thealkylation system by opening valve 54 in line 24 which joins line 2|.Alternately the butane can be discarded by opening valve 55 in line 56.either for use elsewhere or for fractionation of the isoparamnichydrocarbons from the parafilnic hydrocarbons. It should also be obviousthat in the event that isoparamnic hydrocarbons having five and/or sixcarbon atoms per molecule were employed as an isoparaftlnic feed to thea1- kylation reaction these can be taken overhead through line 53 andrecycled through line 24, leaving the alkylate of heavier molecularweight to be withdrawn through line 41.

'I'he polymerization of normally gaseous olefinic hydrocarbons to formdimers, trimers and tetramers thereof, as well as the cross polymers andinterpolymers, is well known in the art. Polymerizer 51 represents anywell known polythrough line 53 to separator 59 wherein a separation ismade between the paranlnic hydrocarbons and the polymers. 'I'hebutane-containing stock passes overhead through line 50 and can bediscarded by opening valve 6I in line -62 or if it contains considerableamounts of isobutane can be directed to alkylation reactor I6 by openingvalve 53 in line 64 which Joins line 2|. The dimers with or withoutheavier polymers which may be present are withdrawn through line anddirected to a prehydrogenator 66 through Vline 61.

The hydrogen containing gas together with the unconverted normallygaseous parailinic hydrocarbons from fractionator 34 and line 44 joinsline 51 prior to prehydrogenator 66. A pump 58 in line 61 aids incompressing the reactants to the desired pressure while heater 69elevates the temperature to the desired range. Prehydrogenation iscarried out at temperatures of from about 200 to about 800 F. and atpressures within the range of from 15 to 5000 pounds persquare inch overa suitable hydrogenating catalyst such as a reduced metal. metal oxideor metal sulfide, including such compounds as reduced copper,nickel-nickel oxide, molybdenum sulilde, and sulded mixed oxides ofmolybdenum, zinc and magnesium. A throughput of from 1 to 10 liquidvolumes per volume of catalyst per hour is suitable with a partiallyreduced supported nickel catalyst; for example, a temperature of about425 F., a pressure of about 50 pounds per square inch, and a rate ofabout three volumes of liquid feed per volume of catalyst per hour, canbe suitably used. With a sulfide catalyst containing molybdenum atemperature of about '100 F., a pressure of about 3000pounds persquareinch, and a rate of about four volumes of liquid feed per volumeof catalyst per hour is preferred. Although this prehydrogenation stepcan perhaps be carried out more rapidly in the presence of pure hydrogenthan when using hydrogen diluted with normally gaseous paraflins, thelatter serves to simplify temperature control of the highly exothermichydrogenation reaction by serving as a diluent and carrying heat fromthev reaction vessel. Such dilution of the reaction mixture smoothes outthe catalyst temperature and raises the yield of hydrogenated polymerdue to elimination of temporary and local hot spots which tend todestructively hydrogenate the feed.

The oleilnic hydrocarbons are preferably present in prehydrogenator 66in excess so that by utilizing all of the hydrogen present from line 44,from about 75 to about 95% of the olefns are hydrogenated in this step.The partially hydrogenated polymers are withdrawn from prehydrogenator66 via line 10 and directed to fractionator 1|, which is maintained atsuitable temperatures and pressures to permit the separation of thenormally gaseous hydrocarbons from the normally liquid hydrocarbons. Apressure reducing valve 12 may be inserted in line 10 prior tomerization process, preferably one employing a Y hydrocarbon fractiondesirably of petroleum origin comprising substantially hydrocarbons hav-4ing four carbon atoms per molecule and containing sufcient quantitiesof normal and/or isobutylenes therein to form dibutylenes in theprocess. `The polymers together with the unreacted paraillnichydrocarbons including normal and isobutanes are withdrawn frompolymerizer' 51 fractionator 1|. The normally gaseous hydrocarbons arepassed overhead from fractionator 1| through line 13 and may bediscarded by opening valve 14 in line 15 or preferably are recycled tothe dehydrogenation step by opening valve 16 in line 11 which joins lineI0. commercially, a small part of the gas isdiscarded, due toimperfections in commercial fractionation equipment, etc.,

through line 15 and the greater part is recycled through line 11. Sincethe hydrogen will have been substantially completely removed inprehydrogenator 66, the overhead gas from fractionator 1I betweenpolymers heavier than that desired for gasoline and those of gasolineboiling tionator 1| will `comprise essentially paramnic i range or theentire partially hydrogenated polymers can be directed to a furtherhydrogenation step. In the event that the heavier polymer is to beseparated, it can be withdrawn through line 1l either for cracking andconversion lto polymers of lower molecular weight or for use elsewhere,while the partially hydrogenated polymers of gasoline boiling range arewithdrawn through line 19 and directed to hydrogenator 80. A pump 8| inline 19 and a heater 82 therein serve to elevate the pressure andtemperature of the partially hydrogenated polymers together with purehydrogen from an outside source which is injected through line 89 to thepoint desirable for carrying out a final hydrogenation of the polymer.Hydrogenator 80 can be maintained at a temperature within the range offrom 250 to 500 F. and pressures of from to 250 pounds per square inchgage and a throughput of 2 to 10 volumes of liquid hydrocarbon pervolume of catalyst per hour. As suitable catalysts we can lemployreduced copper oxide, partially reduced supported nickel oxide orsuliided catalysts similar to those previously described. The preferredconditions are 425 F., about 50 pounds per square inch pressure, and arate of about six volumes of liquid feed per volume of catalyst perhour. The use of considerable excess hydrogen is desirable to saturatecompletely `the polymer and to secure a high reaction rate. I somewhatprefer a low-temperature reduced metal catalyst to a high-temperaturesulde catalyst because of the practically quantitative yields obtained.

Hydrogenated polymer is'withdrawn from hydrogenator 80 through line 84and directed to fractionator 85. Excess hydrogen passes overhead throughline 86 from fractionator 95 and can be discarded by opening valve 81 inline 88, but since its purity remains high it is preferably recycled byopening valve 89 in line 90 which joins line 19. All of the hydrogenatedpolymers can be withdrawn through line 9| and discharged from the systemby opening valve 92 in line 93 or directed to blending tank 2 byopeningvalve 94 in line 95 which joins line 9|. It is also possible, in theevent that both heavyand light polymers were directed to hydrogenator80, to separate these into a fraction of aviation gasoline boilingrangev and a fraction of heavier polymer, the aviation gasoline fractionbeing withdrawn through line 99 and discharged by opening valve 91 inlinev '98 or directed to blending tank 62 by opening valve 99 in line|00, while the heavier polymer is withdrawn from the base offractionator 85 through line 98.

An alternate method is to fractionate thepolymers from polymerizer 51 soas to obtain a fraction boiling within the Vgasoline boiling range, andto subject only thesepolymers to hydrogenation. In this event, separator-59 and fractionatorll can beintercharged. Ait being necessary only toseparate the gases from the prehydrogenated polymers before directingthe latter to final hydrogenator 80.` In such a case, fractionator 86can be replaced by a separator, since there will be no necessity forseparating heavy hydrogenated polymers from gasoline-like material, butonly for the elimination and/or recycle of unconsumed hydrogen.

polymers to saturated hydrocarbons suitable for premium fuels. Forexample. in dehydrogenating ethane within the range Aof conditionsdescribed,- a mixture of approximately 60% ethane,

20% ethylene and 20% hydrogen results. In catalytic alkylation ofisobutane with ethylene. using an aluminum chloride-hydrocarbon complexas a catalyst, feed streams containing as little as 7% ethylene can beused and the ethylene completely removed. There is also a benefit to thecatalyst life due to the presence of appreciable amounts of hydrogen.Using the above dehydrogenated stock, therefore. in alkylation aresidual gas having a composition of approximately 75% ethane and 25%hydrogen is obtained. By recycling this to the dehydrogenation step, s.gas approaching the approximate composition 40% ethane, 40% hydrogen and20% ethylene can be obtained, thus yielding further quantities ofethylene for alkylation. Either the oncethrough or the recycle gas canbe sent to the prehydrogenatlon step. preferably the latter due to itshigher hydrogen content. By thus using the diluted hydrogen for rsthydrogenating an olenic polymer to about -95%, all of the hydrogen isremoved from the stream, while at the same time the synthetic purehydrogen requirements for hydrogenation of the polymers are greatlyreduced. The ethane separated from the partially hydrogenated oleiinicmaterial can be returned tothe dehydrogenation step and the process thusrepeated. Other normallygaseous paratiinic hydrocarbons can be' employedin place of or in admixture with ethane, with equally valuable results.y

By my process normally gaseous peraiiinic hydrocarbons are convertedsubstantially completely to more valuable products in an economic andtrated one preferred embodiment of my invention. I do not intend to belimited thereto, since it 1s by way of example and not by way oflimitation. Moreover, I have omitted various details in apparatus andflow, such as pumps. heat exchangers, valves, control means, reboilers,etc.

all of whichiare well known to those skilled in the art, and which wouldobviously be employed in the commercial utilization of my process.

I claim: l i

1. A process for producing a blended high `oc.\ tane number gasolinewhich comprises the steps dehydrogenating at least a portion of normallygaseous paraillnic hydrocarbons having at least two carbon atoms permolecule to the corresponding olen with the production of hydrogen,subjecting to polymerization gases comprising substantially iso 'andnormal parailinic and oleilnic hydrocarbons having four carbon atoms permolecule, separating av normally liquid polymerization product andunconverted paramnic hydrocarbonavcontacting products from saiddehydrogenation with the unconverted paraillnic hydrocarbons includingisoparaiiinic hydrocarbons separated from the normally liquidpolymerization product, said contacting being in the presence of acatalyst under conditions adapted to promote the alkylation ofisoparamnic hydrocarbons with said olennic hydrocarbons, recovering fromthe total alwlation product a high octane number alkylate Within thegasoline boiling range, recovering a gaseous fraction from said totalalkylation product comprising hydrogen diluted with normally gaseousparafns, catalytically hydrogenating a fraction of the normally liquidolen polymer boiling within the gasoline range in the presence of therecovered hydrogen diluted with normally gaseous parafns adapted topromote the hydrogenaton of said polymer to the extent of between about75% and about 95%, recovering the partially hydrogenated polymer,subjecting the partially hydrogenated normally liquid polymer boilingwithin the gasoline range to a second hydrogenation in the presence ofan excess of substantially pure hydrogen, and blending the completelyhydrogenated normally liquid polymer and the said alkylate to produce ahigh octane number blended gasoline.

2. A process for the production Aof a blended high octane number fuelwhich comprises the steps of heating at least one normally gaseousparaflinic hydrocarbon having at least two carbon atoms per molecule ata temperaturer and pressure adapted to promote the dehydrogenation of atleast a portion of said paraflinic hydrocarbon to the correspondingolefin with the production of hydrogen, subjecting to polymerization a.stream comprising substantially iso and normal paraiiinic and olenichydrocarbons having four carbon atoms per molecule, separating theparainic hydrocarbons and a normally liquid polymerization product,contacting the products from said dehydrogenation including unconvertedparafiinic hydrocarbons, olenic hydrocarbons and hydrogen with theparainic hydrocarbons including isoparaflinic hydrocarbons recoveredfrom the normally liquid polymerization product in the presence of acatalyst under conditions adapted to promote the alkylation of saidisoparaiinic hydrocarbon with said olefinic hydrocarbon, recovering fromthe total alkylation product a high octane number alkylate boilingwithin the gasoline boiling range, recovering a gaseous fraction fromsaid total alkylation product comprising hydrogen diluted with normallygaseous parailins, catalytically hydrogenating a fraction of thenormally liquid olefin polymer boiling within the gasoline boiling rangein the presence of the said hydrogen diluted with normally gaseousparailins whereby the degree of hydrogenation and the temperature of thehighly exothermic hydrogenation reaction are controlled and destructivehydrogenation of the polymer is avoided, recovering the normally gaseousparains from the hydrogenation product, recycling the recovered parafnsto the said dehydrogenation step, hydrogenating the partiallyhydrogenated normally liquid polymer boiling within the gasoline rangewith an excess of substantially pure hydrogen in a separatehydrogenation zone and blending the hydrogenated normally liquid polymerand alkylate boiling within the gasoline range to form a high octanenumber fuel.

3. A process according to claim 1 wherein said isoparaflinichydrocarbons predominate in isobutane.

4. A process according to claim 1 wherein the normally liquidpolymerization product comprises substantially dimers of oleflns havingfour 'carbon atoms per olefin molecule.

, ROBERT F. MARSCHNER.

